Contributors

The following companies have contributed and/or contribute to Btrfs (sorted alphabetically):

• Facebook
• Fujitsu
• Fusion-IO
• Intel
• Linux Foundation
• Netgear
• Novell/SUSE
• Oracle
• Red Hat
• STRATO AG

Jon Corbet (from lwn.net) ran this snapshot of contributors as of 2014/04 (soon after Chris and Josef moved to Facebook):

Top changeset contributors by employer on 2014/04:

Oracle                           1249 (33.2%)
Fujitsu                           613 (16.3%)
Red Hat                           483 (12.8%)
Fusion-IO                         296 (7.9%)
(None)                            288 (7.6%)
Novell/SUSE                       203 (5.4%)
STRATO AG                         152 (4.0%)
Couchbase                         106 (2.8%)
(Consultant)                       62 (1.6%)
(Unknown)                          54 (1.4%)
Intel                              48 (1.3%)
New Dream Network                  36 (1.0%)
Facebook                           31 (0.8%)
IBM                                20 (0.5%)
FOSS Outreach Program for Women    12 (0.3%)
Google                             12 (0.3%)
(Academia)                         11 (0.3%)
Parallels                          11 (0.3%)
HP                                 10 (0.3%)
Datera Inc.                         5 (0.1%)

Source: thread, the stats