[Plugin: Just Custom Fields] WYSISWYG editor doesn't appear in WordPress 3.3

Yeah, this is true. WP changed the way editor works.
Will be fixed in version 1.3 of my plugin

fixed in version 1.3

Fantastic.

Thank you very much for your support. It’s an excellent plugin.

is there a way to add a WYSISWYG editor in a custom textarea?

i want to add tinyMCE

thanks in advance

custom textarea support only wordpress wysiwyg editor by default.
if you want add tinyMCE – you would need to write your own plugin and add hooks and js on post edit page.