<p>I'm making a method combining Scrum with the OpenUP lifecycle and deliverables. I also want to keep the OpenUP disciplines apart from "Project Management".  I can "hide" it so that it's not immediately obvious in my generated method site. But when you then navigate to the "Risk List" artefact for example the PM is still seen as contributing, and if you click on the link, you get taken to the PM Discipline page.</p>

<p>How can I remove it completely from my method without deleting it from the OpenUP library which I'm consuming?</p>

I've never used EPF Composer.
I did a little bit of google searches and I understand what you are looking for can be done through Configurations (select OpenUP in your Library view) and published View definitions.
See slide 83 and 84 of this PPT document. You should be able to take it from there.
An Introduction to the Eclipse Process Framework
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In case the link does not work, I searched for "EPF Composer" "Standard categories" on google and the document is at the bottom of the first results page.
Good luck.