Don't Crack for a limited time have set free Bus Driver, a free Vintage Optical Compressor with Tube Saturation.
From the Don't Crack website:
Bus-Driver is an optical compressor that provides a wide range of compression effects, reminiscent of the best vintage compressors made in the ‘60s.
Also included in Bus Driver is a Tube-Driver Saturation feature. It allows you to add the sound of a vintage tube amplifier giving you the differing electronic characteristics of triode, tetrode, and pentode vacuum tubes. So you can add the vintage warmth of the those models of the classic tubes (e.g. ECC83, 12AX7, etc..) to your tracks or on your mix bus.
AAX Native, RTAS, AudioUnit, and VST. 32/64-bit.
Use voucher code 'freebusdriver' (without quotes).