Probably an encoding issue in their localization files. If you want English labels, you could simply replace the zhTW locale with the enUS locale.
1. Find the localization files. For TSM, for example, these are in a "Locale" subfolder.
2. Open the enUS.lua file. Copy everything after the AceLocale registration code, which should look something like this:
Code:
local L = LibStub("AceLocale-3.0"):NewLocale("TradeSkillMaster", "enUS", true)
if not L then return end
3. Open the zhTW.lua file. Replace everything after the AceLocale registration code with the code you copied from the enUS.lua file in the previous step.
4. Done. This should give you enUS localization for the addon.