Snowball stemmer supports many languages other than english, but does porter also?
PorterStemmer was for English. However, the author, Porter himself, extended his work Snowball for English as well as other languages. This is one reason why many use SnowBall for other languages.
Here is a quote from Wikipedia:
Many implementations of the Porter stemming algorithm were written and freely distributed; however, many of these implementations contained subtle flaws. As a result, these stemmers did not match their potential. To eliminate this source of error, Martin Porter released an official free software (mostly BSD-licensed) implementation of the algorithm around the year 2000. He extended this work over the next few years by building Snowball, a framework for writing stemming algorithms, and implemented an improved English stemmer together with stemmers for several other languages.