I’m afraid that’s it, the whole point of selling in the EW is that there are no rbz to manually install, and the licencing system is managed by the warehouse.
therefore, if you use an older version of sketchup, even if in theory it could be compatible, you can’t install it. and even if you could (by installing on SU26 then copying the install files to you SU17), the licencing system allowing you to use it is in the extension warehouse.
Now, some of Eneroth’s plugins are also on Sketchucation. Sketchucation has a different (independant) licencing system.
if it’s not available here, and you’re stuck with SU17, you’ll have to find another similar plugin I’m afraid.
edit : I guess Mihai is using Fredo Joint PushPull, and it works. and it’s on sketchucation 