since there's no context, one has no other choice...it's like a university exam...
first we back ourselves up here:
http://en.wikipedia.org/wiki/Kielbasa
I've seen it spelled all ways as listed in the wiki link...I always hated (the spelling) kielbasa, but these name variations don't really represent the different versions, it's closer to brand and marketing...
I certainly don't recommend sausage, while it is generally acurate, we Americans see sausage differently, and this brief phrase induces images of Polish style "kielbasa". And if anybody knows a good Italian sausage purchase locale in Prague, do let me know.

As far as the half in parenthesis, if this is not a label where accuracy is pertinent, I'ld leave "half-" off, why resolve what percentage of ham?, and who know's what the other half may even be? Some things we don't want to know...for such a general term one can only conjure up the image of the type..found at Kaufland = "sunkova klobasa"

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Note added at 28 mins (2011-03-13 17:33:48 GMT)
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Actually upon consideration, it really doesn't matter if it's 35% or 75% ham, the adjectival form of ham, ham, suffices to describe it's main attribute...a bacon burger ends up being probably 2-3% total weight of the burger...but it's a bacon burger, to be sure...

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Note added at 29 mins (2011-03-13 17:34:32 GMT)
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its, not it's :)