I just ran it on Oracle 9.2.0.5 and it always returns 1. :)
SQL> select 1 from dual where 1/0=42 or 1=1;
1
----------
1
SQL> edit
Wrote file afiedt.buf
1 select 1 from dual
2* where 1=1 or 1/0=42
3 ;
1
----------
1
SQL> edit
Wrote file afiedt.buf
1 select 1 from dual
2* where 1=1 or 1/(select count(*) from all_tables where table_name = 'NOTHING')=42
3 ;
1
----------
1
SQL> edit
Wrote file afiedt.buf
1 select 1 from dual
2* where 1/(select count(*) from all_tables where table_name = 'NOTHING')=42 or 1=1
3 ;
1
----------
1
SQL>
I hope this doesn't mean that Oracle is exceptional or rather exceptionless. :)