Ao olhar para link , podemos ler
Tomcat 6.0 requires JRE 5.0. Read the RELEASE-NOTES and the RUNNING.txt file in the distribution for more details.
Se você abrir o RELEASE-NOTES, verá
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Dependency Changes:
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Tomcat 6.0 is designed to run on JSE 5.0 and later.
Então deve estar bem.