All of G.D.T.'s download links are partially dead, but can still be recovered through the Wayback Machine. I will post all of the links for the characters and stages here for ease of access purposes.
Ryu - https://web.archive.org/web/20160427185139/http://jamsgoegoe.sitemix.jp/mugen/HostedChars/ssf2x_ryu.zip
Ken - https://web.archive.org/web/20160427185114/http://jamsgoegoe.sitemix.jp/mugen/HostedChars/ssf2x_ken.zip
Fei Long - https://web.archive.org/web/20160427184657/http://jamsgoegoe.sitemix.jp/mugen/HostedChars/ssf2x_feilong.zip
Cammy - https://web.archive.org/web/20160427184819/http://jamsgoegoe.sitemix.jp/mugen/HostedChars/ssf2x_cammy.zip
Akuma / Gouki - https://web.archive.org/web/20160427184927/http://jamsgoegoe.sitemix.jp/mugen/HostedChars/ssf2x_gouki.zip
Dictator's Stage - https://web.archive.org/web/20230306234903/http://jamsgoegoe.sitemix.jp/mugen/HostedStages/ssf2x_vega.zip
As for Violent Ken, he's still M.I.A. as far as I know. I did find a version of him uploaded by namesomething over on Mugen Archive, but it seems as though it has been slightly edited by luis dossman and zadkiel, so the original is still lost. I have decided to upload this version of Violent Ken over on Mediafire since Mugen Archive links are not allowed here. You can find that here for anyone curious: https://www.mediafire.com/file/bw1waaci11xci39/Violent_Ken.rar/file