Whats an MDL?

MDL files are the last stage of bootup process: first the KERNEL starts, then various servers start (on UIQ phones, startup sequence can be read in QSTART.RSC file; don't know about the others), and finally INSTREC is run, which INSTalls all RECognizers, i.e. MDL files, each one of them defines a MIME type and/or starts an application. Here on newlc.com there is a good article about MDL: look for EZBOOT.

Like other application  but with mdl as targettype in your mmp.

For a very good example have a look to EzBoot on NewLC...