For me this is an ideal GTD implementation. In my GTD mindmap I can organise my actions anyway I want (by area in my life, by project, as a sub-task). In the generated next actions lists I can find back my actions organised by context. In other Freeplane GTD systems (or GTD systems with other mindmap software) organising by context often involves multiple entries of the same action or filtering. The last option is quite OK, but how do you carry it around with you? With Freeplane|GTD I can print the next action list and carry them around. Also I can print them as a PDF file (with PDFCreator) and put them on my smartphone with Dropbox. By the way, I also use Dropbox for making available my GTD mindmap at home and at my work. A nice feature is that if you click an action in the list it will be selected in the mindmap. The last thing I discovered is that I can link actionable Gmail and Outlook messages to my mindmap actions. (This is not a specific Freeplane|GTD feature.) Now I do not have to keep separate lists in my e-mail systems.
Go to youtube and search for GTD and freeplane. You'll find a bunch of how tos there to get you started quickly.