You don't need it. You'll probably already have it...
Curl bindings come as
standard with FreePascal and is under packages/libcurl.
A little while ago (less than a year) I submitted a patch to get the examples working for Windows too (applied in trunk by Florian) and at that time I also checked en tested if there was major funtionality missing: there wasn't.
It may have a refresh when I have time, but there really is no need for it except for SSL protocol related support that definitely needs updating. I have some internal patches for that, but it still needs work at places I don't need myself and it has no priority.
IOW: Curlpas is outdated but the standard version in FPC isn't. The libcurl standard one that is included with FPC is recently tested and compiles without errors for all platforms for which libcurl is supported.
If you need help (e.g. enabling a recent feature) , plz ask: there are not many people that use curl on Pascal Platforms, they rather tend to use Pascal native solutions like fcl-web (also standard) or synapse. But I use it myself sometimes.
Note that basic URL support is also in Lazarus as standard and takes just the inclusion of lclintf in your project: GetURL etc.... Just as convenient.