some info:

firebird 1227 0.0 0.0 3536 4 ? S Feb21 0:00
/opt/firebird/bin/fbguard -f
firebird 1228 0.0 0.5 22568 3088 ? S Feb21 0:00
/opt/firebird/bin/fbserver
firebird 1229 0.0 0.5 22568 3088 ? S Feb21 0:00
/opt/firebird/bin/fbserver
firebird 1232 0.0 0.5 22568 3088 ? S Feb21 0:01
/opt/firebird/bin/fbserver

ISQL Version: LI-V1.5.1.4481 Firebird 1.5
groups: juser firebird
/home/juser is group writeable

firebird.conf: #DatabaseAccess: full (so I guess it's the default)

I can connect to the server and run queries but I can't create
databases, some things I've tried:

-----------------------------------------------------
SQL> connect '/opt/firebird/examples/employee.fdb' user 'SYSDBA'
password 'masterkey';
Database: '/opt/firebird/examples/employee.fdb', User: SYSDBA
SQL> show tables;
COUNTRY CUSTOMER
DEPARTMENT EMPLOYEE
EMPLOYEE_PROJECT JOB
PHONE_LIST PROJECT
PROJ_DEPT_BUDGET SALARY_HISTORY
SALES
SQL>

[juser@pclin juser]$ sh /opt/firebird/bin/createAliasDB.sh newdb
/home/juser/newdb.fdb
/opt/firebird/bin/createAliasDB.sh: /opt/firebird/bin/createAliasDB.
sh: Permission denied

[juser@pclin juser]$ /opt/firebird/bin/isql -u SYSDBA -p masterkey
Use CONNECT or CREATE DATABASE to specify a database
SQL> create database '/home/juser/newdb.fdb' user 'SYSDBA' password
'masterkey';
Statement failed, SQLCODE = -902

I/O error for file "/home/juser/newdb.fdb"
-Error while trying to create file
-Permission denied
SQL>

[juser@pclin juser]$ /opt/firebird/bin/isql -u SYSDBA -p masterkey
Use CONNECT or CREATE DATABASE to specify a database
SQL> create database '/home/juser/newdb.fdb' user 'SYSDBA' password
'masterkey';
Statement failed, SQLCODE = -902

I/O error for file "/home/juser/newdb.fdb"
-Error while trying to create file
-Permission denied
SQL>

[juser@pclin juser]$ /opt/firebird/bin/isql
Use CONNECT or CREATE DATABASE to specify a database
SQL> create database '/home/juser/newdb.fdb' user 'SYSDBA' password
'masterkey';
Statement failed, SQLCODE = -902

I/O error for file "/home/juser/newdb.fdb"
-Error while trying to create file
-Permission denied
SQL> create database 'localhost:/home/juser/newdb.fdb' user 'SYSDBA'
password 'masterkey';
Statement failed, SQLCODE = -902

I/O error for file "/home/juser/newdb.fdb"
-Error while trying to create file
-Permission denied
SQL>
---------------------------------------------

Now I don't know what to do, please help me.
(not running firebird as root of course)