I bought the SoundFont in 2014 as far as I know it is still available to buy online. My favorite commercial SoundFont is the official 4 MB Gravis UltraSound Plug & Play one (this is different from the 5.6 MB GUS Classic patch set). I do like gm.dls's cheesy/ghostly choir sound though, and I think it fits some MIDIs better than the SC-55's more realistic choir. The Synth Strings, Sweep, and Halo instruments for example sound nowhere near as good as they do on the hardware. Additionally, I think gm.dls's synth and pad instruments sound extremely dull compared to most other SoundFonts (and especially the SC-55). For example, the 'DOOM' voice heard in the intro to DOOM II MAP05's music does not play correctly with gm.dls.
Gm.dls's samples are noticeably lower quality than the real SC-55's, and some instruments sound completely different.