is it possible to use tinymce editor with blojsom 2.30?

That too. Though now I fully understand some hiccups you might run into...

For instance, if you secure your administration interface with HTTPS (setting the blog-admin-url property in blog.properties) on a different URL than "www", things will not behave properly. See http://tinymce.moxiecode.com/punbb/viewtopic.php?id=829 for the ugly details related to TinyMCE, and http://www.mozilla.org/projects/security/components/same-origin.html to details the JS security model in mozilla lineage browsers. Bottom line, you may have to edit the admin templates and rebuild the jar to accommodate.

Example:

If you have a HTTPS domain like "http://secure.myawesomeblog.com/blojsom/blog/default?flavor=admin" TinyMCE expects a "www" domain, and some components will fail. 

You can use a relative path to get around this however (if the templates mentioned do not already use a relative path, be prepared to rebuild the jar).