scoreexchange.com, former sibeliusmusic.com requires .sib files. How to convert to .sib ???

Without buying Sibelius! So this looks like a good place to post my creations ( I also post here on musescore.org, on soundcloud, dropbox, and scribd), but this looks like a file share site devoted to music. Ooops, only for sibelius users!

I've been browsing around, looking for some utility that will create .sib files, but I guess that's proprietary secret info held by sibelius company.

Anybody else looked at scoreexchange.com? Or is there some other good place to share music, like scribd, but for music?

Thanks.