I just "Download + Load" mtpaint, which was posted a few minutes ago for TC6.x x86, on Tiny Core 6.2 with Openbox via Apps GUI.
Like it was reported in the 6.2RC thread, WBar disappears after loading some extensions.
Also there is no Openbox menu entry created for mtpaint. Instead this file is left in /tmp.
<item label="mtpaint" icon="/usr/local/share/pixmaps/mtpaint.png"> <action name="Execute"> <command>mtpaint</command> </action> </item>