3
This article mentions two fees:
Is the credit line fee one time or per credit line? Are there any other fees in Ripple? Is there a place that summarizes all the different fees, both inherent in the protocol and determined by gateways/users? This answer is rather comprehensive, but it doesn't mention fees for credit lines nor the number '50', so it isn't be complete.
4
The answer you cited discusses the fees that can be charged on fiat currencies by gateways, when exchanging currencies, and when using other users to swap IOUs. The XRP fees are imposed by the network itself.
The transaction fee is the only fee that is destroyed. Currently, it is 10 drops per transaction under normal load conditions. (A drop is a millionth of a Ripple.)
The fees you mentioned are actually reserves. Reserves are amounts of XRP you must hold to maintain an entry in the ledger. The reserve is returned when the entry is removed, however, there is no way to remove an account. The reserve is not destroyed, it stays in the account. You can use your reserve to pay transaction fees. You just can't create a new entry if you don't have the reserve to cover it.
Currently, the only entries that require a 50 XRP reserve are credit lines and offers. It is expected that future entries, such as contracts, will also require a reserve. A credit line only counts towards your reserve under some circumstances. Other people can't extend credit to you and increase your reserve.
1Perhaps someone should contact Bitcoin Magazine and ask them to explain that the fees are actually reserves - their article is rather accurate and comprehensive, it's a shame to leave such a mistake. Is the 50 XRP required per credit line? – ripper234 – 2013-02-26T21:53:47.833
2It's per credit line if you created the credit line and under some other circumstances. But nobody else can extend credit to you and thereby raise your reserve. – David Schwartz – 2013-02-26T22:13:20.727
I assume multiple credit lines of different currencies to the same entity don't count as one line, right? – ripper234 – 2013-02-27T03:52:17.720
BTW, I'm surprised that you don't upvote Ripple questions more often. – ripper234 – 2013-02-27T03:52:57.500
2@ripper234: Each credit line counts if you extend credit, including different currencies from the same issuer. – David Schwartz – 2013-02-27T21:02:04.017
Has the unit's name been changed from "drop" to "drip" now ? – Alex Kravets – 2013-02-27T23:36:47.187
@AlexKravets: It should be "drop"! Fixed now. – David Schwartz – 2013-02-27T23:49:22.063
1That was a nice Freudian slip related to the XRP distribution process :-) – Alex Kravets – 2013-02-27T23:50:12.640