I simply can't figure out when we write open source and when open-source. Here is a couple of examples where I'm not sure which one to use:

Kaboodle is an open-source (open source?) application.

Open-source developers (or open source?) developers.

Microsoft Office faces stiffer competition from the open-source (or open source?) world.

I've tried to find an answer in Oxford Style Guide to no avail, and Google was no help either.

I'd really appreciate it, if anyone could clarify this one for me.

Thank you!

Kind regards,
Hello Dimitri, and welcome to English Forums. In this type of hyphenation problem, you are likely to find more than one opinion, but I would suggest that the safest path-- i.e. the clearest presentation-- is to hyphenate when it is an attributive adjective (that is, when it precedes its noun):

Kaboodle is an open-source application. ('open-source' is an attributive adjective)
Kaboodle's application is open source. ('open source' is a predicate adjective)
Kaboodle's application comes from (is?-- what do I know about sources??) an open source. ('source' is a noun)

The bottom line is that you need to hyphenate when there is a possibility of confusion as to which word relates to which, as in:

Kaboodle is an open source sensitive software application. (I don't know what that means-- but my point is, is it 'open-source sensitive' or 'open source-sensitive' or 'open-source sensitive-software'?)

If there is potential for confusing the reader, hyphenate.
I agree with Mister Micawber. In my opinion he's exactly right.

As a general rule, English is lacking in rules, so you should do your best to make your writing unambiguous!

Endaksi; Emotion: smile
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Hi Mister Micawber,

Thank you for your detailed reply. It's all make sense to me now.

I've just discovered English Forums, an it's a real treasure trove.

Kind regards,
 Eimai_Anglos's reply was promoted to an answer.
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