Inclusion Criteria:

          -  Patients must have histologically confirmed indolent B-cell NHL or mantle cell
             lymphoma; acceptable subtypes of indolent B-cell NHL include follicular lymphoma
             (grades 1, 2, or 3a), marginal zone lymphoma, or lymphoplasmacytic
             lymphoma/Waldenstrom's macroglobulinemia; patients with mantle cell lymphoma must have
             a documented t(11;14) or overexpression of cyclin D1 by immunohistochemical
             evaluation; patients with active large cell transformation are not eligible; however,
             patients with a history of large cell transformation are eligible provided that there
             is no current clinical evidence of active transformed lymphoma

          -  Eastern Cooperative Oncology Group (ECOG) performance status 0-2

          -  At least one prior therapy; prior autologous or allogeneic stem cell transplant is
             allowed; patients may not be on chronic immunosuppressive therapy for
             graft-versus-host disease (GVHD); patients who have received prior treatment with a
             pan-selective PI3K inhibitor are not eligible; however, prior therapy with a selective
             PI3K inhibitor, Bruton's tyrosine kinase inhibitor, or other B-cell receptor targeting
             agents is allowed

          -  Serum creatinine =< 2.0 mg/dL

          -  Total bilirubin =< upper limit of normal

          -  Aspartate aminotransferase (AST)/alanine aminotransferase (ALT) =< 2.0 x upper limit
             of normal

          -  Absolute neutrophil count (ANC) >= 750/mm^3

          -  Platelets >= 50,000/ mm^3

          -  Serum lipase =< upper limit of normal

          -  Serum amylase =< upper limit of normal

          -  International normalized ratio (INR) =< 2.0

          -  Fasting glucose < 120mg/dL

          -  Recovery to =< grade 1 toxicities associated with prior therapy

          -  Negative serum pregnancy test; if, on cycle 1 day 1, greater than 72 hours has elapsed
             since the last negative result, a serum pregnancy test must be repeated and be
             negative on cycle 1 day 1 (C1D1) for the patient to remain eligible

          -  Patient has the ability and willingness to provide informed consent and has signed the
             informed consent document

        Exclusion Criteria:

          -  Pregnant or breast-feeding women and women of childbearing age or men who are
             unwilling to use adequate contraception; females of childbearing age and potential
             (i.e., not surgically sterilized) must use a second form of contraception, including
             total abstinence, intra-uterine device, double-barrier contraception, or other
             non-hormonal form of contraception

          -  Patients with a history of central nervous system involvement by lymphoma

          -  The presence of co-existing medical conditions that would limit compliance with study
             medications, including, but not limited to active infection, active or untreated
             cardiac or pulmonary disease, or malignancy

          -  Patients with significant, symptomatic deterioration of lung function confirmed by
             spirometry, diffusion capacity of carbon monoxide (DLCO), or resting oxygen (O2)
             saturation

          -  Patients with impairment of gastrointestinal function that may alter the absorption of
             BKM120

          -  Patients currently being actively treated or who have been treated within the past 3
             years for an unrelated malignancy (except non-melanoma skin cancer, cervical carcinoma
             in-situ, and low risk prostate cancer)

          -  Patients who have undergone major surgery within 2 weeks prior to study enrollment or
             who have not recovered from a major surgery

          -  Patients with known human immunodeficiency virus (HIV), hepatitis B or hepatitis C
             (active or carriers)

          -  Patients with a fasting blood glucose >= 120 mg/dL (6.7mmol/L); patients with diabetes
             mellitus are eligible if they require oral agents only and have a fasting blood
             glucose =< 120 mg/dL; patients with a history of diabetes mellitus who require daily
             long-acting or mealtime insulin are not eligible; patients who have previously
             required treatment for hyperglycemia due to steroids or other medications are eligible
             as long as they have not required insulin or any other oral agent within 2 months
             prior to study enrollment

          -  Patients who are on chronic steroids for unrelated conditions (i.e. rheumatologic
             conditions) are not eligible if their total daily dose of steroids is >= 10mg
             prednisone

          -  Patients with a known hypersensitivity to BKM120 or its excipients

          -  Patients with active moderate or severe major mood or psychiatric disorder as judged
             by the investigator, primary care physician, counselor, psychiatrist, or as a result
             of the patient's mood assessment questionnaire that may interfere with the ability to
             comply with the trial; in addition, given the prior mood-associated toxicities,
             patients with a history of psychiatric hospitalization within the past 5 years,
             electroconvulsive therapy (ECT) within the past 5 years, or whose psychiatric
             condition has been unstable within 2 months prior to study enrollment requiring
             addition or change of psychotropic medications are not eligible; examples include, but
             are not limited to:

               -  Medically documented history of or active major depressive episode requiring
                  inpatient or intensive outpatient therapy, bipolar disorder (I or II),
                  obsessive-compulsive disorder, schizophrenia, a history of suicidal attempt or
                  active ideation, or homicidal ideation (immediate risk of doing harm to others);
                  patients under the care of a primary care physician who are treated with one oral
                  agent and who have not required dose adjustments or new medications within 2
                  months prior to study enrollment and who otherwise meet eligibility requirements
                  may be enrolled

               -  >= Common Terminology for Adverse Events (CTCAE) version 4.0 grade 3 anxiety

               -  Patients meeting the cutoff score of >= 12 in the Patient Health Questionnaire-9
                  (PHQ-9) or a cut-off of >= 15 in the Generalized Anxiety Disorder-7 (GAD-7) mood
                  scale, respectively, or who select a positive response of "1, 2, or 3" to
                  question number 9 regarding potential for suicidal thoughts in the PHQ-9
                  (independent of the total score of the PHQ-9) are not eligible

          -  Patients with diarrhea >= CTCAE grade 2

          -  Patients with active cardiac disease including any of the following:

               -  Left ventricular ejection fraction < 50% as determined by multi gated acquisition
                  scan (MUGA) scan or echocardiogram

               -  Corrected QT interval (QTc) > 480 msec on screening ECG (using the QTcF formula)

               -  Active angina pectoris

               -  Ventricular arrhythmias except for benign premature ventricular contractions

               -  Supraventricular or nodal arrhythmias or any conduction abnormality requiring a
                  pacemaker or automatic implantable cardioverter defibrillator (AICD)

               -  Valvular disease with documented compromise in cardiac function

               -  Symptomatic pericarditis

               -  Myocardial infarction within the past 6 months

               -  Congestive heart failure (New York Heart Association [NYHA] functional
                  classification III-IV)

          -  Patients who are currently receiving treatment with medications with a known risk to
             prolong the QT interval or inducing Torsades de Pointes and the treatment cannot
             either be discontinued or switched to a different medication prior to study enrollment

          -  Patients who have taken herbal medications and certain fruits within 7 days prior to
             study enrollment are not eligible; herbal medications include, but are not limited to,
             St John's wort, Kava, ephedra (ma huang), gingko biloba, dehydroepiandrosterone
             (DHEA), yohimbe, saw palmetto, and ginseng; exclusionary fruits include the cytochrome
             P450 family 3, subfamily A, polypeptide 4 (CYP3A) inhibitors Seville oranges,
             grapefruit, pummelos, or exotic citrus fruits

          -  Patients who are currently treated with drugs known to be moderate and strong
             inhibitors or inducers of isoenzyme CYP3A, and the treatment cannot be discontinued or
             switched to a different medication prior to study enrollment; (please note that
             co-treatment with weak inhibitors of CYP3A is allowed)

          -  Patients who have received oral or IV chemotherapy, targeted anticancer therapy or
             radiation therapy =< 4 weeks (6 weeks for nitrosourea, antibodies or mitomycin-C)
             prior to study enrollment

          -  Patients who are currently taking therapeutic doses of warfarin sodium or any other
             Coumadin-derivative anticoagulant; patients who can be safely changed to enoxaparin or
             other non-warfarin derived anti-coagulant and who otherwise meet eligibility
             requirements may be enrolled