Texmaker 4.0.4 had been ported (2013/08/30)
ftp://ftp.netlabs.org/pub/qtapps/texmaker-4.0.4-os2.7z

Texmaker is a free, modern and cross-platform LaTeX editor for os2 systems that integrates many tools needed to develop documents with LaTeX, in just one application.
Qt Ports Page: http://svn.netlabs.org/qtapps/wiki/QT4%20Office
Project URL: http://www.xm1math.net/texmaker/index.html
Port by Elbert Pol.
Source: OS/2 Warp News and Rumors