의외로 답은 가까이에 있군요..

혹시 저와 같이 헤매시는 분들이 계실것 같아 이렇게 글을 올립니다.

이 사이트의  팁&트릭에 올라와 있는 자료
http://firebird.borlandforum.com/impboard/impboard.dll?action=read&db=fb_tutorial&no=11
http://firebird.borlandforum.com/impboard/impboard.dll?action=read&db=fb_tip&no=7

그리고, 외국 사이트를 조금 뒤져보니 해답이 나오네요^^
http://forums.devshed.com/firebird-sql-development-61/access-denied-for-udf-s-in-firebird-embedded-2-0t-418124.html

관심을 가져 주신 여러분들께 다시 한번 감사드립니다.

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Installing an Embedded Server Application
Application Root
Just copy fbembed.dll, icudt30.dll, icuin30.dll and icuuc30.dll into the directory with your application
exectable.
You should also copy firebird.msg and firebird.conf (if necessary) to the same directory.
Note
You will need firebird.conf only if it is necessary to set some non-default configuration parameter
for the embedded server.
If external libraries are required for your application, such as INTL support (fbintl.dll and
fbintl.conf) or UDF libraries, create subdirectories beneath the application root for them, emulating
the Firebird server ones, e.g. /intl or /udf, respectively.
Rename fbembed.dll
Rename fbembed.dll to either fbclient.dll or gds32.dll, according to which is required by your
database connectivity software.
Start your application
Now start your application and it will use the embedded server as a both a client library and a
server and will be able to access local datasases via the XNET network emulation protocol.
Installation Structure Examples
...
c:\my_app\icudt30.dll
c:\my_app\icuin30.dll
c:\my_app\icuuc30.dll
c:\my_app\firebird.conf
c:\my_app\firebird.msg
c:\my_app\intl\fbintl.dll
c:\my_app\intl\fbintl.conf
c:\my_app\udf\fbudf.dll        <= 이대로 하시면 됩니당~ㅅㅅ
Suppose you want to place the Firebird files (excluding the renamed fbembed.dll) in another directory.
In that case, you need to modify your firebird.conf and set RootDirectory to the Firebird directory
tree that is parent to the Firebird files.
Example
c:\my_app\app.exe
c:\my_app\gds32.dll
c:\my_app\ib_util.dll
c:\my_app\icudt30.dll
c:\my_app\icuin30.dll
c:\my_app\icuuc30.dll
c:\my_app\firebird.conf
d:\fb\firebird.msg
d:\fb\intl\fbintl.dll
d:\fb\intl\fbintl.conf
d:\fb\udf\fbudf.dll
In firebird.conf:
RootDirectory = d:\fb