The Remastered Star Frontiers rules are gone along with 14 of the 25 issues of Star Frontiersman Magazine, as the issues in question contained remastered articles from TSR's Dragon Magazine and such.
Note: WotC had given permission for the sites to host the original TSR published material, but as WotC is now releasing Star Frontiers material from the TSR days as PDFs on RPGNow, having such material available for free elsewhere doesn't make good business sense.
There ARE, however, some download links that still work as of this morning:
Tenkar's Tavern is supported by various affiliate programs, including Amazon, RPGNow, and Humble Bundleas well asPatreon. Your patronage is appreciated and helps keep the lights on and the taps flowing - Your Humble Bartender, Tenkar
Tenkar's Tavern Discord Server Events - link - https://discord.gg/fReGmuD - Click to embiggen