If you are looking for a $0 download that replicates the G-Master’s functionality (Auto-release, "Glue" characteristics), these community favorites are the gold standard:
If you want the SSL sound without a time limit, these freeware plugins are highly recommended by pros: SSL Native Bus Compressor 2 - Solid State Logic Ssl G-master Buss Compressor Free - Download
These plugins mimic the character, VCA response, and "Auto-Release" features of the original SSL G-Series hardware: If you are looking for a $0 download
: Emulates the unique Integrated Circuit (IC) input and twin Voltage Controlled Amplifier (VCA) design of the original hardware. Signature Controls It adds a bit of harmonic saturation (color)
If you want something that looks and feels more like hardware, the developer Analog Obsession offers incredible free plugins. Their "BussPressor" is designed explicitly to emulate that classic 4000 series behavior. It adds a bit of harmonic saturation (color) that ReaComp might lack, giving you that "warm" analog feel instantly.
: A classic freeware VCA compressor based on the SSL design. It is known for its "Shaping" control, which allows you to adjust the speed of the compressor's attack for more or less punch .